Self-Oscillating Optical Frequency Comb: Application to Low Phase Noise Millimeter Wave Generation and Radio-Over-Fiber Link

Abstract

A self-oscillating optical frequency comb generator (SOFCG) is demonstrated by applying optoelectronic loop feedback to an optical frequency comb generator (OFCG) based on a dual-drive Mach-Zehnder modulator. The resulting SOFCG provides 23 comb lines with a frequency spacing of 11.84 GHz, corresponding to the oscillation frequency defined by the optoelectronic loop. The corresponding OFCG is also implemented by replacing the optoelectronic feedback loop with a microwave synthesizer at 11.84 GHz. A 94.8 GHz mm-wave signal is then generated by selecting two tones and heterodyning in a high speed photodetector for both the SOFCG and the OFCG. The SOFCG system offers superior single sideband phase noise performance compared to the OFCG approach. Using the SOFCG developed here it is possible to generate mm-wave signals up to 260 GHz, and this method is applicable to multiband radio-over-fiber (RoF) links. A radio-over-fiber link is implemented with the SOFCG at 94.8 GHz. An LTE Advanced OFDM FDD 64-QAM signal of 20 MHz bandwidth is transmitted over a 1.3 m wireless distance with an error vector magnitude (EVM) of 2.23%.

Self-Oscillating Parametric Optical Frequency Comb Generation Using an Electroabsorption Modulated Laser-Based Optoelectronic Oscillator

“…This is because the output signals of a high-frequency RF synthesizer are usually derived from frequency multiplication of a low-frequency quartz oscillator, which also multiplies the phase noise [14]. To overcome this limitation, some schemes of self-oscillating OFC generators have been proposed and experimentally demonstrated [14]- [16]. In these works, an EOM-based OFC generator is embedded in an optoelectronic oscillator (OEO) topology, where the generated optical comb is photo-detected to produce a microwave output to drive the modulators.…”

“…So, no frequency synthesizer is required, and the phase noise of the RF driving signal is low and frequency-independent [14]. An MZM and a PM are cascaded in the oscillation loop to generate optical frequency combs in [15], while a dualdrive MZM is used in [16]. Large-signal RF inputs are fed back to these modulators to generate more sidebands [8], [16].…”

“…An MZM and a PM are cascaded in the oscillation loop to generate optical frequency combs in [15], while a dualdrive MZM is used in [16]. Large-signal RF inputs are fed back to these modulators to generate more sidebands [8], [16]. Alternatively, a monolithic OFC generator consisting of a PM and a Fabry-Perot (FP) resonator has been employed to replace the conventional EOMs in the OEO loop [14].…”

Tunable THz Signal Generation and Radio-Over-Fiber Link Based on an Optoelectronic Oscillator-Driven Optical Frequency Comb

“…OFCGs based on external modulators, a microwave synthesizer is used to provide the seed tone and to determine the frequency spacing. However, it is possible to dispense with an external RF source by driving the OFCG with an OEO instead (either directly or via a self-oscillating approach [14], [15]) for subsequent low-phase noise generation of mm-wave and THz signals. In [16], a photonic microwave generation technique was demonstrated by using a dual-polarization quadrature phase shifting keying (DP-QPSK) modulator.…”

“…The self-oscillating OFCG reported in [14] and [15] lacks the frequency tunability of a conventional OEO and hence the mm-wave and THz signal frequency can only be tuned by changing the selected lines spacing. Recently in [17], we experimentally demonstrated the photonic generation of mmwave and THz signals using a tunable OEO driven OFCG.…”